The present invention relates to an apparatus for controlling an internal combustion engine, and in particular to an apparatus for controlling an internal combustion engine which is capable of effectively purifying harmful components in an exhaust gas emitted from the engine at the initial phase of starting of the engine with a purifying catalyst disposed in an exhaust system. In a broad aspect, the invention relates to an apparatus for controlling the amount of a fuel supplied to an internal combustion engine.
The exhaust gas emitted from internal combustion engines contains harmful components, such as carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx). These harmful components have an adverse influence upon the human body as air pollutants and hinder the growth of plants.
In order to reduce the amount of these harmful components contained in the exhaust gas emitted from an internal combustion engine, researches for purifying the exhaust gas emitted from internal combustion engines have been conducted to provide in exhaust system of the engine with an exhaust gas purifying catalytic converter including a three way catalyst to remove pollutants exhaust gas.
Although the amount of the harmful components in the exhaust gas can be reduced by providing the exhaust system with an exhaust gas purifying catalytic converter, the exhaust gas purifying ability is exhibited only after the catalyst has been elevated to a temperature at which it becomes active. The exhaust gas purifying ability of the catalyst before activation is very low so that harmful components are discharged into the atmosphere until the catalyst is heated to a temperature at which it becomes active.
The temperature at which the exhaust gas purifying catalyst becomes active depends upon the composition of the catalyst and is usually 250.degree. to 400.degree. C. as described in Japanese Unexamined Patent Publication Tokkai-Sho 54-16018.
Approximately two minutes or a longer period of time is normally required for the catalyst gas to be heated to 250.degree. to 400.degree. C. following the starting of an engine. Some literature, such as Japanese Unexamined Patent Publication Tokkai-Sho 54-79319, say that it takes 3 to 5 minutes.
Therefore, it is important matter to determine how to effectively purify the harmful components in an engine exhaust gas emitted during the several minutes following starting of the engine until the catalyst is heated to an active temperature.